The invention concerns a photographic copying apparatus. It further concerns a process for the operation of such a photographic copying apparatus.
In professional photographic laboratories at the present time, photographic copies--paper images--, for example, of exposed and developed negatives, are produced largely by fully automatic photographic copying apparatuses, the so-called printers. The operating personnel, in the case of such devices, essentially performs monitoring functions, controls the exposure process and maintains a continuous working process to the extent possible. For this purpose, the operating personnel is concerned with the copy material--for example unexposed and exposed photographic paper--and in particular must make certain that sufficient master material--exposed and developed negative film--is always available for further processing, and that the already processed negative film is removed in time from the copy apparatus in order to avoid unnecessary downtimes of the photographic copy apparatus. In advanced photographic copy devices, the negative films to be processed further are spliced together into long strips of negative films and wound onto supply spools supplied on the inlet side to the copy apparatus.
A strip of negative film is threaded on the inlet side into the film transport path and transported automatically through the copy apparatus. Following its passing through the processing station, for example, the exposure station, in which the negative is exposed onto unexposed photographic paper, the strip of negative film is again wound onto a winding spool located on the outlet side of the copy apparatus. When the rear end of the negative film strip leaves the supply spool, the operating personnel must replace the empty supply spool with a full one. However, in the meantime, the rear end also passes through the processing station and is drawn out of the film transport path and wound onto the winding spool. The operating personnel must therefore take care that the winding spool, which now is full, is replaced by an empty one as soon as possible.
The downtime of the copy apparatus depends essentially only on the reaction and manipulation time of the operating personnel. The operating personnel must therefore be ready at the exact moment, or otherwise the copy apparatus will be at a standstill for an unnecessary length of time. At the present time the operating personnel usually operates several devices simultaneously, such that exact timing is necessary, which in turn requires a very high degree of attention on the part of the personnel; in particular, the fill level of the film spools on the inlet and the outlet sides must be monitored accurately. There is hardly any time left for the rest of the tasks, for example the change of paper cassettes. In particular, in the transition to photographic copy apparatuses with an hourly capacity of 15,000 or more images, these tasks often cannot be performed at all, as for example the replacement of the film spools on the inlet side may take longer than the passage of the remaining negative film strip through the copy apparatus.
To eliminate this problem, it is proposed in U.S. Pat. No. 4,919,354 (corresponding to DE-A-3 737 788) to provide two storage and two winding spools at the inlet and the outlet side of the copy apparatus, said spools to be set on stub arbors located in a mirror image plane relative to the film transport plane, above each other. On the inlet side, each of the two supply spools is provided with its own feed and threading device. Each of the feed and threading devices comprises a pair of rollers consisting of a counter pressure roller fixedly mounted on the apparatus and an advance roller. Between the counter pressure rollers a wedge shaped switch is provided. At the end of the switch opposing the counter pressure rollers, a pivoting rocker is located; it carries the advance rollers driven in opposing directions, one of which is always abutting in each terminal position of the rocker against the corresponding counter roller. While for example the negative film strip is being reeled off the lower supply spool, a second supply spool may be set upon the second axle. The front end of the negative film strip is inserted manually between the rocker and the corresponding counter pressure roller. By actuating the rocker, the corresponding advance roller is pivoted against the counter pressure roller and the front end of the film is clamped in. All of the negative film strip is reeled off the lower supply spool and wound onto the winding spool. Only then is the advance roller associated with the upper supply spool activated and the new negative film strip threaded into the film transport path. During the reeling off of the negative film strip from the upper supply spool another supply spool is set onto the lower stub arbor in analogous manner, and so on.
On the outlet side again, two winding spools are provided for the negative film strip; they may be set onto two stub arbors, in an approximate mirror image plane relative to the film transport plane. Each of the two winding spools, which must be special catch rollers, is provided with a pivoting catch arm for the front end of the negative film strip. These catch arms are of a special design and guide the front end of the film to the catch spool desired.
While the layout proposed of two supply spools on the inlet side and two winding spools on the outlet side makes it possible for the operating personnel to replace, at any given time during the reeling off of the negative film strip from the working supply spool and the winding of the negative film strip, the empty second spool with a new full supply spool and the second full winding spool with a new empty one, the copy apparatus proposed has certain essential disadvantages capable of improvement. On the inlet side for each supply spool separate threading and feed devices, each containing a counter pressure roller and an advance roller, and a switch, are required. A separate drive motor is provided for each advance roller. The rocker carrying the two advance rollers must be reset manually or manually operated setting elements must be provided, to actuate a pneumatic reversing device. On the outlet side, the copy apparatus configuration is also complex. A separate pivoting catch arm is required for each winding roller to hold the front end of the film. The pivoting of the catch arms again requires separate drive motors and control devices. The entire configuration of the copy apparatus on the inlet and outlet side is thus relatively complex and requires excessive attention by the operating personnel for additional manipulating steps. Beyond this, the personnel must always be careful so that in each instance the correct supply or winding spool is being replaced (i.e., once the upper spool and then the lower one, etc.). A very great disadvantage consists of the fact that only special spools designed as catch spools may be used. However, an essential disadvantage of this state of the art copy apparatus primarily consists in that the negative film strip being processed must always be first completely withdrawn from the film transport path before a new one may be threaded in.